Question

Which of the following processes is an example of an isothermal process?

• A. A gas expanding with no heat exchange and increasing temperature.
• B. A gas expanding at constant temperature.
• C. A gas compressed rapidly causing temperature to rise.
• D. A gas heated at constant volume.

Hint:

The prefix "iso-" means equal, and "-thermal" refers to temperature.
Thus, "isothermal" always corresponds to a process where temperature is maintained constant throughout.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
This question asks for the definition or a clear example of an isothermal thermodynamic process.

Step 2: Key Formula or Approach:
An isothermal process is defined as a thermodynamic change of state during which the temperature of the system remains constant:
\[ T = \text{constant} \quad \Rightarrow \quad \Delta T = 0 \]
For an ideal gas, the equation of state is $PV = mRT$, which means $PV = \text{constant}$.

Step 3: Detailed Explanation:

• Option A describes an adiabatic-like process but with temperature variations, which is not isothermal.

• Option B explicitly states "at constant temperature", which perfectly matches the definition of an isothermal process.

• Option C represents a rapid compression (often modeled as adiabatic), where temperature increases.

• Option D represents an isochoric heating process where temperature rises.

• Therefore, only a process occurring at a constant temperature qualifies as isothermal.

Step 4: Final Answer:
A gas expanding at constant temperature is an example of an isothermal process.